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Varnish Clam (Nuttallia obscurata)

Varnish clams (Nuttallia obscurata). Photo credit: Graham Gillespie.

Varnish clams (Nuttallia obscurata). Photo credit: Graham Gillespie.

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Species overview

Physical description

Varnish Clam is a medium-sized intertidal clam. It has two thin shells that are oval in shape. Its shells are attached by a large hinge on the outside. The outside of Varnish Clam shells is coated in a thick, brown layer known as a periostracum. This layer covers the chalky, purplish-white shell underneath.

Varnish Clam shells are:

The inside of Varnish Clam shells is purple, from deep royal purple to light violet. Its flesh is white. Varnish Clam likely grows at a similar rate to Manila Clam reaching 38 millimeters (mm) long in about 4 years. It can grow at least 69 mm long. It lives for at least 6 years.

Distribution 
Varnish Clam is native to:

It was accidentally introduced to Canada in the late 1980s in ballast water. It has been reported in Barkley Sound on the west coast of Vancouver Island since 1997. In less than 10 years, Varnish Clam spread to most beaches in the Georgia Strait. Today, Varnish Clam ranges from the Central Coast of British Columbia (BC) to Oregon.

Varnish Clam burrows in:

Varnish Clam burrows down to 30 centimetres (cm) deep. It can bury deeper than Littleneck and Manila clams because of it has a longer siphon. This reduces competition for space. Because it burrows more deeply than Manila Clam, its harvest can disrupt Manila Clam.

Varnish Clam prefers living near:

Varnish Clam habitat overlaps with several other species including:

Life cycle

Male Varnish Clams as small as 16 mm have sperm. Female Varnish Clams as small as 23 mm have eggs. This suggests that maturity occurs in the first year of life. In BC, spawning occurs between early June and September.

Varnish Clam is a broadcast spawner, meaning males and females release eggs and sperm into the water for fertilization. Unlike native clams, female Varnish Clams leave puddles of eggs on the sea floor that can be fertilized later. After eggs hatch, larvae are pelagic for several weeks.

Fishery history

Varnish Clam was harvested commercially on a small scale in the early 2000s. It was marketed as Savoury Clam. Varnish Clam is not currently harvested as part of the commercial intertidal clam fishery.

Varnish Clam may be farmed or harvested by permitted aquaculture tenure owners or operators in BC. There is a very limited market for Varnish Clam.

There are few opportunities to harvest Varnish Clam recreationally in BC. Interest in it is low compared to other species of intertidal clam.

Ecosystem context

Varnish Clam is a filter feeder. It uses its siphon to remove food particles from the water column. Feeding only happens when Varnish Clam is underwater. When the tide is low, Varnish Clam closes its shells tightly and waits to feed until the tide covers it again.

Bivalve shellfish are very sensitive to water quality because they feed by filtering microscopic organisms from the water. While feeding, harmful bacteria, viruses, and marine biotoxins can build up in their tissues. If eaten, this can make humans sick.

Be careful when harvesting shellfish. Check for contamination in the subarea where you plan to harvest. Check our real-time bivalve shellfish safety harvesting map. If there are no contamination closures, check species regulations and additional harvest restrictions.

Varnish Clam is also a pedal feeder, meaning it eats organic waste from sediment using its foot. This reduces competition for food with other filter feeding clams.

Varnish Clam is eaten by:

Varnish Clam hosts juvenile Pea Crabs, sometimes with high infestation rates.

Science advice and research

Science advice and research for Varnish Clams

Integrated Fisheries Management Plan

Integrated Fisheries Management Plan for Intertidal Clams

Sources

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